The invention relates to a mobile crane with a main jib luffably mounted thereon and able to be raised via a luffing cylinder, and with a main jib extension releasably connected to a main jib head of the main jib via upper bolts and lower bolts, the main jib extension, starting from a basic position after release of the upper bolts, is able to be angled about a luffing axis relative to the main jib by means of an angling drive, the angling drive engages on a foot of the main jib extension, wherein a lifting mechanism of the mobile crane, which is provided for another task, provides the movement energy for the angling drive.
The invention also relates to a method for angling a main jib extension relative to a main jib of a mobile crane, wherein the main jib is luffably mounted on the mobile crane and can be raised via a luffing cylinder, the main jib extension is releasably connected to a main jib head of the main jib via upper bolts and lower bolts and an angling drive engages on a foot of the main jib extension.
German utility model DE 20 2004 020 760 U1 already discloses a mobile crane with a main jib and a main jib extension fastened to its main jib head. The main jib extension is luffable from a basic position, in which the main jib extension is oriented with its longitudinal direction as an extension of the longitudinal direction of the main jib, into a 20° position and a 40° position. In a conventional manner, the main jib extension is releasably fastened to the main jib head via two lower bolts disposed in the region of bottom chords of the main jib extension and two upper bolts disposed in the region of top chords of the main jib extension. In order to be able to luff the main jib extension about the two lower bolts serving as a luffing axis out of the basic position, in a first step the two upper bolts are pulled and in a second step, by means of hydraulic luffing cylinders which engage on the main jib head and on the main jib extension, the luffing of the main jib extension is effected. The insertion and pulling of the two upper bolts is effected in each case via a hydraulic bolting cylinder. In order to power the luffing cylinders and the bolting cylinders an autonomous hydraulic assembly is disposed at the lower end of the main jib extension. It is possible to use e.g. a diesel engine or an electric motor, in each case with an associated hydraulic pump, as the hydraulic assembly.
German patent specification DD 291 531 A5 relates to a mobile crane with an angling plate between a main jib and a main jib extension, wherein the main jib extension, starting from a basic position after release of a holding bolt, can be angled by means of an angling drive about a luffing axis. The movement energy required for this is supplied by a lifting cable of the mobile crane.
A mobile crane with a main jib is also known from the German laid-open document DE 10 2009 010 452 A1. A lifting cable is inter alia used to mount and dismount a main jib extension to/from the main jib.